CN114829258A

CN114829258A - System and method for balancing at least one parameter to be balanced of an electric motor of a propulsion system

Info

Publication number: CN114829258A
Application number: CN202080085744.1A
Authority: CN
Inventors: 大卫·勒梅; 让-菲利普·雅克·马林
Original assignee: Safran Helicopter Engines SAS
Current assignee: Safran Helicopter Engines SAS
Priority date: 2019-12-09
Filing date: 2020-12-09
Publication date: 2022-07-29
Also published as: WO2021116606A1; JP2023505394A; EP4072944A1; US20220411091A1; FR3104138A1; CA3158594A1; IL293637A; EP4072944B1; IL293637B2; KR20220106989A; FR3104138B1

Abstract

A system (11) for balancing at least one parameter to be balanced of an electric motor of a propulsion system (1), in particular of an aircraft, comprising at least two electric motors (3, 4) and a propulsion member (2) driven in rotation by said electric motors. The balancing system is configured to calculate a correction of the speed setpoint (Corr _ Cons _ VI, Corr _ Cons _ V2) as a function of a correction factor of the speed setpoint (F1, F2) and of the speed setpoint (Cons _ VH) of the propulsive member (2), this correction factor being dependent on a parameter of the associated electric motor (P1, P2) intended to be balanced.

Description

System and method for balancing at least one parameter to be balanced of an electric motor of a propulsion system

Technical Field

The present invention relates to the field of aircraft propulsion systems, such as in particular electric or hybrid aircraft propulsion systems.

Background

An electric or hybrid aircraft propulsion system includes a propulsion member configured to enable and/or participate in propulsion and/or lifting of an aircraft, and at least two electric motors configured to drive rotation of the propulsion member. The propulsion member may be a propeller (e.g. a streamlined or non-streamlined propeller), a turbojet fan, or more generally any propulsion member driven by at least two electric motors.

The number of electric motors used to drive the propellers is generally large in order to be able to achieve rotation of the propellers and thus propulsion and/or lifting of the aircraft in the event of failure of one of the electric motors.

The electric motors may be arranged in series on the same drive shaft or by means of a mechanical coupling or gear engagement system and are kinematically coupled, wholly or partially in a rotary manner, to the propellers. Thus, in at least one mode of operation, the rotational speed of the electric motor is proportional to the rotational speed of the propeller.

Typically, each of these electric motors is controlled individually. Two control modes may be used to control the motors individually.

According to a first control mode, the speed of the propulsion member is directly controlled in common for all electric motors. Thus, the motors are controlled according to a single speed control loop that is directly related to the speed of the propeller. In this case, the so-called overall speed control of the propulsion members makes it possible to calculate the torque control set point of each electric motor. Therefore, each electric motor is individually controlled in terms of torque.

According to a second control mode, the motors may be controlled in torque according to a particular torque control loop for each motor. This mode of control makes it possible to ensure the safety of the aircraft in the event of failure of one of the electric motors.

For each of these electric motors, the control system of the motor according to the respective speed of the motor comprises an autonomous control circuit independent of the other motors. Thus, propeller speed control is robust to failure of one of the control loops and/or the electric motor. Furthermore, in the event of decoupling of the propeller, the electric motor speed control is maintained, which facilitates the re-coupling of the propeller.

However, in such decentralized speed control systems (i.e. specific to each electric motor), differences in the power supplied by each motor are observed. This difference in supplied power is mainly due to the fact that: the motor is not configured to be naturally balanced and may cause significant overheating of the electric motor supplying the highest power and therefore degradation of the motor, or even failure of said motor.

Therefore, it is necessary to balance the power supplied by the electric motors driving the same rotating shaft of the propeller.

In order to balance the electric motors, it is known to establish communication between the electric motors. However, the number of connections required for such communication is proportional to the number of motors, which makes the propulsion system more complex. Furthermore, handling such communication failures is particularly difficult.

Therefore, there is a need to balance the electric motors of a propulsion system while enhancing the independence between the motors.

Disclosure of Invention

It is therefore an object of the present invention to overcome the disadvantages of the above-mentioned systems and to propose a system and a method for balancing the different electric motors of an aircraft propulsion system without any communication between these electric motors.

The present invention therefore relates to a system for balancing at least one parameter to be balanced for an electric motor of a propulsion system, in particular of an aircraft, comprising at least two electric motors and a propulsion member or propeller driven in rotation by said electric motors.

It will be noted that the driving torque of the propulsion member preferably varies monotonically with its rotational speed, which is typically the case for propulsion members used in aircraft.

The balancing system comprises balancing modules associated with the electric motors, each of these balancing modules being configured to calculate a correction of the speed setpoint as a function of a correction factor of the speed setpoint and of the speed setpoint of the propulsive member, this correction factor being dependent on a parameter of the associated electric motor intended to be balanced.

Thus, the balancing is therefore specific to each motor and only one or more parameters of the controlled motor are used.

It will be noted that the invention is not limited to the number of motors described with reference to the figures and can be applied to N electric motors, N being an integer greater than two.

The correction factor for the speed setpoint is, for example, a decreasing monotonic affine function (decreasing monotonic affine function) which depends on the balancing gain and a predetermined maximum setpoint correction value.

The balancing gain may be determined according to a maximum value of the static error over the speed of the propulsion member allocated for balancing the electric motor (the maximum value being predetermined, for example, according to a maximum rotational speed set point of the propulsion member), a minimum value of the static error over the speed of the propulsion member allocated for balancing the electric motor (the minimum value being predetermined, for example, according to a minimum rotational speed set point of the propulsion member), and a maximum value and a minimum value of the parameter to be balanced.

The balancing gain is determined so as to reduce the static error between the parameters of the electric motor intended to be balanced and, therefore, on the speed of the propulsive member.

According to an embodiment, the balancing system comprises a module for compensating for static errors in the speed of the propulsive member, the module being configured to calculate a compensation setpoint for the speed setpoint of the propulsive member as a function of the parameter to be balanced of the associated motor.

According to another embodiment, the balancing system comprises a module for compensating for static errors in the speed of the propulsive member, the module being configured to calculate a compensation setpoint for the speed setpoint of the propulsive member as a function of the estimated load value of the propulsive component.

The parameter to be balanced corresponds, for example, to the current in the associated electric motor.

The parameter P to be balanced corresponds to a basic physical quantity for the design of the electric motor and may be selected from a list which is not exhaustive and comprises the torque delivered by the electric motor, the current in the electric motor, the current consumed by the power electronics of the electric motor, the mechanical power, the electric power at a point in the propulsion chain, e.g. the temperature measured on the electric motor.

For example, the balancing system comprises a low-pass filter upstream of each balancing module in order to filter the parameters of the associated electric motor entering the balancing module intended to be balanced.

According to a second aspect, the invention relates to a control system comprising a balancing system as described above and a control module associated with the electric motor and configured to calculate a torque command as a function of the rotation speed of the associated electric motor and of a speed setpoint calculated by the balancing system and to send the torque command to the associated electric motor.

Advantageously, the control system comprises two separate control units, each control unit being assigned to an electric motor, each of these control units comprising at least a balancing module and a control module.

According to another aspect, the invention relates to a propulsion system, in particular of an aircraft, comprising at least two electric motors mounted on the same rotation shaft, a propulsion member or propeller driven in rotation by said motors, and a system as described above for controlling the electric motors.

According to another aspect, the invention relates to a method for balancing at least one parameter to be balanced of an electric motor of a propulsion system, in particular of an aircraft, the propulsion system comprising at least two electric motors and a propulsion member or propeller driven in rotation by said electric motors, the method comprising:

-a step of calculating a correction factor for the speed set point, the correction factor depending on the parameters of the associated electric motor intended to be balanced, an

-for each of these electric motors, a step of calculating a correction of the speed setpoint as a function of the calculated correction factor and of the speed setpoint of the propulsive member.

Advantageously, for calculating the correction factor of the speed set point, the balancing gain is calculated according to a maximum value of the static error on the speed of the propulsive member allocated for balancing the electric motor (this maximum value being predetermined, for example, according to a maximum rotational speed set point of the propulsive member), a minimum value of the static error on the speed of the propulsive member allocated for balancing the electric motor (this minimum value being predetermined, for example, according to a minimum rotational speed set point of the propulsive member), and a maximum value and a minimum value of the parameter to be balanced.

According to an embodiment, the compensation setpoint of the speed setpoint of the propulsive member is calculated according to the parameter to be balanced of the associated motor or according to an estimated load value of the propulsive member.

According to another aspect, the invention relates to a control method, wherein the speed set point calculated in the calculation step of the balancing method as described above is sent to a control module associated with the electric motor and the torque command is calculated as a function of the speed of rotation of the associated electric motor and said speed set point.

Thus, the control method is configured to adjust the speed set point of each of the motors according to the speed set point correction factor calculated by the balancing method.

Drawings

Other objects, features and advantages of the present invention will appear upon reading the following description, given by way of non-limiting example only, with reference to the accompanying drawings, in which:

figure 1 schematically shows an aircraft propulsion system according to a first embodiment of the invention, comprising two electric motors and a system for controlling said motors, the system comprising a system for balancing parameters of said motors;

FIG. 2 is a graph showing a rotational speed set point correction of a motor of the propulsion system on the y-axis, according to a parameter of said propulsion system on the x-axis;

FIG. 3 shows a method for controlling an electric motor of the propulsion system of FIG. 1, including a method for balancing parameters of said motor implemented in the balancing system of FIG. 1;

figure 4 schematically shows an aircraft propulsion system according to a second embodiment of the invention, comprising two electric motors and a system for controlling said motors, the system comprising a system for balancing parameters of said motors; and

fig. 5 schematically shows an aircraft propulsion system according to a third embodiment of the invention, comprising two electric motors and a system for controlling said motors, the system comprising a system for balancing parameters of said motors.

Detailed Description

In fig. 1, an aircraft propulsion system 1 is very schematically represented, comprising a propeller 2, which enables and/or participates in the propulsion and/or lifting of the aircraft; and two electric motors 3, 4 configured to drive the rotation of the propeller 2 by means of coupling and/or gear engagement devices 5, 6. It is to be noted that the present invention is not limited to the number of motors described with reference to the drawings, and may be applied to N motors, N being an integer greater than two.

Furthermore, the present invention is not limited to the presence of coupling and/or gear engagement devices. The electric motors 3, 4 may be arranged directly on the shaft of the propeller 2.

It will also be noted that the motors 3, 4 may be separate equipment items, each consisting of a stator and a rotor, a single motor member consisting of several multi-phase stator windings and a common rotor, or any combination of the above elements.

The propulsion system 1 also comprises a control system configured to calculate a torque command Cons _ C1, Cons _ C2 and to send it to each of the electric motors 3, 4.

The control system 10 comprises two separate control units 10a, 10b, each assigned to an electric motor 3, 4. Each control unit assumes the balancing and control functions of the associated motor. The control electronics itself may also form part of the electric motor. Such motors are referred to as "smart".

Alternatively, a single electronic control unit may be provided for both electric motors.

The control system 10 is configured to modify the torque command of each electric motor 3, 4 according to the parameters P of the associated electric motor intended to be balanced, for example according to the power delivered by the corresponding motor.

For this purpose, control system 10 comprises a balancing system 11 configured to calculate a correction Corr _ Cons _ V1, Corr _ Cons _ V2 of the speed setpoint of the associated electric motor 3, 4 as a function of correction factors F1, F2 of the speed setpoint, the correction factors F1, F2 depending on the parameter P of the associated electric motor intended to be balanced. Thus, balancing is specific to each motor, and only one or more parameters of the controlled motor are used.

The parameter P to be balanced corresponds to a basic physical quantity for the design of the electric motor and may be chosen from a list that is not exhaustive and comprises the torque delivered by the electric motor, the current in the electric motor, the current consumed by the power electronics of the electric motor, the mechanical power, the electrical power at a certain point in the kinematic chain, for example the temperature measured on the electric motor.

In all the embodiments shown and described, the parameter P to be balanced corresponds to the current in the electric motor. In practice, the current corresponds to a fundamental parameter for the design of the electric motor, and in particular the power electronics of the electric motor. Balancing the currents in the electric motor makes it possible to optimize the design of the electric motor and to reduce the temperature of the electric motor. It will be noted that the invention is not limited to the use of the current in the motor as the parameter to be balanced, and may be applied to any parameter to be balanced as defined above.

As shown, the balancing system 11 comprises a first balancing module 12 associated with the first electric motor 3 and a second balancing module 13 associated with the second electric motor 4.

The first balancing module 12 is configured to calculate a correction Corr _ Cons _ V1 of the speed setpoint as a function of the speed setpoint Cons _ VH of the propeller and of a first correction factor F1. The first correction factor F1 depends on the parameter P1 to be balanced, here the current in the first electric motor 3. The speed setpoint Corr _ Cons _ V1 is then sent to the control module 14 of the speed V1 of the first electric motor 3, which is configured to calculate a torque setpoint Cons _ C1 as a function of the rotation speed V1 of the first electric motor 3 and of the speed setpoint Corr _ Cons _ V1 calculated by the balancing module 12.

Similarly, the second balancing module 13 is configured to calculate a correction Corr _ Cons _ V2 of the speed setpoint as a function of the speed setpoint Cons _ VH of the propeller and of the second correction factor F2. The second correction factor F2 depends on the parameter P2 to be balanced, here the current in the second electric motor 4. The speed setpoint Corr _ Cons _ V2 is then sent to the control module 15 of the speed V2 of the first electric motor 4, which is configured to calculate a torque command Cons _ C2 as a function of the rotation speed V2 of said second motor 4 and of the speed setpoint Corr _ Cons _ V2 calculated by the balancing module 13.

In the case where the propulsion system 1 comprises N electric motors, each of the balancing modules of the associated electric motor is configured to calculate a correction Corr _ Cons _ VN of the speed set point according to the following equation:

Corr_Cons_VN＝Cons_VH+F

wherein:

FN is a decreasing monotonic affine function expressed according to the following equation:

FN＝Corr_Cons_Vmax+GN.PN

wherein:

GN is the balance gain of each electric motor; and

corr _ Cons _ Vmax is a predetermined maximum set point correction value corresponding to a maximum static error in the speed set point of the propeller that is allowed to occur to balance the motor.

The balancing gain GN is determined so as to reduce a static error E in the speed of the propeller 2, which is proportional to the parameters of the motor to be balanced (here the current).

The equilibrium gain GN is expressed according to the following equation:

wherein:

emax is the maximum value of the static error in the speed of the propeller allocated for balancing the electric motor, which is predetermined according to the maximum rotational speed setpoint of the propeller; the static error is imposed on the propulsion system by the aircraft flight control system, and depends on the precision required by the piloting system to ensure stable, comfortable and effective flight control for the pilot;

emin is the minimum value of the static error in the speed of the propeller allocated for balancing the electric motor, predetermined according to the minimum rotational speed setpoint of the propeller; the minimum static error, like the maximum static error, is imposed on the propulsion system by the aircraft flight control system;

pn (max) is the maximum value of the parameter to be balanced, here the maximum value of the current allowed by the electric motor N; and

pn (min) is the minimum value of the parameter to be balanced, here the minimum value of the current of the electric motor N.

An excessive balance gain GN results in a deterioration of the speed control stability margin of the motor N, potentially leading to electric motor oscillation. It is therefore important to determine the balancing gain in order to obtain a compromise between the balancing mass of the electric motor, the static error induced on the speed of the propeller and the robustness of the stability of the overall motor control.

To compensate for this drawback, the control system 10 may comprise a low-pass filter upstream of each balancing module, in order to filter the parameter P to be balanced (here the current) entering the motor of the balancing module.

The first electronic control unit 10a includes a first balancing module 12 and a first control module 14.

The second electronic control unit 10b comprises a second balancing module 13 and a second control module 15.

The control system thus comprises two separate control units assigned to the electric motors.

Fig. 2 shows a graph illustrating the rotation speed set point correction of the electric motors 3, 4 of the propulsion system 1 on the y-axis according to the parameters P1, P2 to be balanced for each motor 3, 4 on the x-axis.

Line D1 corresponds to a balancing line corresponding to a correction of the speed set point imposed on each electric motor according to the parameter P to be balanced (here the current in the motor).

In this graph, an example of the trend of the operating point of an electric motor balanced according to the first embodiment described above is represented, in order to show the interaction between the balancing function, the parameter to be balanced and the correction of the speed set point. The operating points Pt1 and Pt2 correspond to initial operating points of the first electric motor 3 and the second electric motor 4, respectively.

In the embodiment shown, the first electric motor 3 initially has a low current, while the second electric motor 4 initially has a higher current than the current of the first motor.

The balancing module 12 associated with the first motor 3 is configured to correct the speed set point of said motor in order to increase the current of this motor.

Conversely, the balancing module 13 associated with the second motor 4 is configured to correct the speed set point of said motor in order to reduce the current of this motor.

Thus, the balancing system 11 is configured to move the operating points of the electric motors close to each other. The residual current deviation E _ P between the electric motors is proportional to the speed measurement error E _ V between said motors.

Thus, the current deviations are significantly reduced without eliminating all these deviations.

The flow chart represented in fig. 3 shows an embodiment of a method 20 for controlling the electric motors 3, 4, comprising a method 21 for balancing the parameters of said motors implemented in the balancing system of fig. 1.

The balancing method 21 comprises a step 22 of calculating a correction factor F1, F2 of the speed set point, which depends on the parameters P1, P2 of the associated electric motor intended to be balanced; and a step 23 of calculating, for each of the electric motors 3, 4, a correction Corr _ Cons _ V1, Corr _ Cons _ V2 of the speed set point from the correction factor and the speed set point Cons _ VH of the propeller 2, according to math 1 to math 3 of the above equation.

The control method 20 also comprises a step 24 of sending the speed set points Corr _ Cons _ V1, Corr _ Cons _ V2 calculated in the calculation step 23 of the balancing method 21 to the

control module

14, 15 associated with one of the electric motors 3, 4; and a step 25 of calculating torque commands Cons _ C1, Cons _ C2, or directly duty command PWM of the motors, as a function of the rotation speeds V1, V2 of the associated electric motors 3, 4 and of said speed set points Corr _ Cons _ V1, Corr _ Cons _ V2.

The embodiment shown in fig. 4 (in which like elements have like reference numerals) differs from the embodiment shown in fig. 1 in that: a module 16a, 16b for compensating static errors is integrated in each of these control units 10a, 10 b.

Each of the modules 16a, 16b for compensating the static error is configured to calculate a compensation setpoint Cons _ comp of the setpoint of the propeller 2 from the estimated value charge _ H of the load of the propeller 2.

The estimated value charge _ H of the load of the propeller 2 is known from the propeller manufacturer, in particular using a map according to the pitch of the propeller and the rotational speed of the propeller.

The compensated set point Cons _ comp of the set point of the propeller 2 is then sent to the input of each of the balancing

modules

12, 13 of the balancing system 11.

Each of these modules 16a, 16b makes it possible to partially compensate in open loop for static errors in the speed of the propeller.

However, the estimation of the load of the propeller is not a constant value.

The embodiment shown in fig. 5 (in which like elements have like reference numerals) differs from the embodiment shown in fig. 1 in that: upstream of the electronic control units 10a, 10b assigned to each of the electric motors, a module 17 for compensating static errors in the control system 10 is integrated. For example, the module 17 for compensating the static error may be integrated in a control unit configured to calculate the speed setpoint Cons _ VH of the propeller.

The module 17 for compensating the static error is configured to calculate a compensation setpoint Cons _ comp of the setpoint of the propeller 2 according to the parameter P to be balanced (here the current).

modules

12, 13 of the balancing system 11.

The module 17 makes it possible to fully compensate in closed loop for static errors in the speed of the propeller without communication between the electric motors.

The modules 16 and 17 of the second and third embodiments of the invention make it possible to apply a back regulation of the speed set-point applied by the balancing module.

Thanks to the invention, the electric motors do not communicate with each other, but with a given electronic control unit 10a, 10 b. Such communication is already present on the aircraft propulsion system, so that the proposed solution does not make the propulsion system more complex.

The invention may be applied to any propulsion system comprising a propulsion member and at least two electric motors mounted on the same rotational shaft of the propulsion member.

The term "propeller" as used more specifically in the detailed description of the drawings generally encompasses any propulsion member driven by at least two electric motors. In other words, the propulsion member may be a propeller (for example of the streamlined or non-streamlined propeller type) or a turbojet fan.

Claims

1. A system (11) for balancing electric motors of a propulsion system (1), in particular of an aircraft, with at least one parameter (P1, P2), said propulsion system comprising at least two electric motors (3, 4) and a propulsion member (2) driven in rotation by said electric motors, characterized in that said balancing system (11) comprises balancing modules (12, 13) associated with each electric motor (3, 4), each of said balancing modules (12, 13) being configured to calculate a correction of a speed setpoint (Corr _ Cons _ V1, Corr _ Cons _ V2) as a function of a correction factor (F1, F2) of the speed setpoint and a speed setpoint (Cons _ VH) of said propulsion member (2), said correction factors (F1, F2) being dependent on said at least one parameter (P1, P1) of the associated electric motor intended to be balanced, P2).

2. The balancing system (11) according to claim 1, wherein the correction factor (F1, F2) of the speed set point is a decreasing monotonic affine function depending on a balancing Gain (GN) and a predetermined maximum speed set point correction value (Corr _ Cons _ Vmax).

3. A balancing system (11) according to claim 2, wherein the balancing Gain (GN) is determined as a function of a maximum value (Emax) assigned for balancing a static error on the speed of the propulsion member (2) of the electric motor, a minimum value (Emin) assigned for balancing the static error on the speed of the propulsion member (2) of the electric motor, and a maximum value (pn (max)) and a minimum value (pn (min)) of the parameter (P) to be balanced.

4. The balancing system (11) according to any one of the preceding claims, comprising a module (16a, 16b) for compensating the static error (E) on the speed of the propulsive member (2), said module being configured to calculate a compensation setpoint (Cons _ comp) of the speed setpoint (Cons _ VH) of the propulsive member (2) as a function of an estimated value (Charge _ H) of the load of the propulsive member (2).

5. The balancing system (11) according to any one of claims 1 to 4, comprising a module (17) for compensating the static error (E) on the speed of the propulsive member (2), configured to calculate a compensation setpoint (Cons _ comp) of the speed setpoint (Cons _ VH) of the propulsive member (2) as a function of the parameters (P1, P2) to be balanced of the associated motor.

6. The balancing system (11) according to any of the preceding claims, wherein the parameters (P1, P2) to be balanced correspond to the current in the associated electric motor (3, 4).

7. The balancing system (11) according to any one of the preceding claims, comprising a low-pass filter upstream of each balancing module, so as to filter the parameters (P1, P2) of the associated electric motor entering the balancing module intended to be balanced.

8. A control system (10) comprising a balancing system (11) according to any one of the preceding claims and a control module (14, 15) associated with an electric motor (3, 4) and configured to calculate and send to the associated electric motor (3, 4) a torque command (Cons _ C1, Cons _ C2) as a function of the rotation speed (V1, V2) of the associated electric motor (3, 4) and of the speed setpoint (Corr _ Cons _ V1, Corr _ Cons _ V2) calculated by the balancing system (11).

9. The control system (10) according to claim 8, comprising two separate control units (10a, 10b), each assigned to an electric motor (3, 4), each of the control units (10a, 10b) comprising at least a balancing module (12, 13) and a control module (14, 15).

10. A propulsion system (1), in particular of an aircraft, comprising at least two electric motors (3, 4) mounted on the same rotation shaft, a propulsion member (2) driven in rotation by said motors (3, 4), and a system (10) according to claim 8 or 9 for controlling said electric motors.

11. Method (21) for balancing an electric motor of a propulsion system (1), in particular of an aircraft, with at least one parameter (P1, P2) to be balanced, the propulsion system comprising at least two electric motors (3, 4) and a propulsion member (2) driven in rotation by the electric motors, the method comprising:

-a step (22) of calculating a correction factor (F1, F2) of the speed set point, said correction factor depending on the parameters (P1, P2) of the associated electric motor intended to be balanced, and

-for each of said electric motors (3, 4), a step (23) of calculating a correction of the speed setpoint (Corr _ Cons _ V1, Corr _ Cons _ V2) as a function of the calculated correction factors (F1, F2) and of the speed setpoint (Cons _ VH) of said propulsive member (2).

12. Method of balancing (21) according to claim 11, wherein, for calculating the correction factors (F1, F2) of the speed set point, a balancing Gain (GN) is calculated as a function of the maximum value (Emax) of the static error over the speed of the thrust member (2) allocated for balancing the electric motor, the minimum value (Emin) of the static error over the speed of the thrust member (2) allocated for balancing the electric motor, and the maximum value (pn (max)) and the minimum value (pn (min)) of the parameter (P) to be balanced.

13. Balancing method (21) according to claim 11 or 12, wherein a compensation setpoint (Cons _ Comp) of the speed setpoint (Cons _ VH) of the propulsive member (2) is calculated according to the parameter (P1, P2) to be balanced of the associated motor, or according to an estimate (Charge _ H) of the load of the propulsive member (2).

14. A control method (20) of electric motors (3, 4), wherein the speed set points (Corr _ Cons _ V1, Corr _ Cons _ V2) calculated in the calculation step (23) of the balancing method (21) according to any one of claims 11 to 13 are sent to the control modules (14, 15) associated with the electric motors (3, 4), and torque commands (cors _ C1, Cons _ C2) are calculated as a function of the rotation speeds (V1, V2) of the associated electric motors (3, 4) and the speed set points (Corr _ Cons _ V1, Corr _ Cons _ V2).